Science 9: Unit E: Science 9: Unit E: Space ExplorationSpace Exploration

Topic 4: Topic 4: Bigger and Smarter Bigger and Smarter TelescopesTelescopes

Bigger TelescopesBigger Telescopes

A limitation of early telescopes was that they were A limitation of early telescopes was that they were too small to see that far into space.too small to see that far into space.

Beginning in the 1700s bigger and bigger telescopes Beginning in the 1700s bigger and bigger telescopes were built to see more detail in the universe.were built to see more detail in the universe.

Sir Herschel Walker used a huge telescope and used Sir Herschel Walker used a huge telescope and used it to discover Uranus, the first planet discovered it to discover Uranus, the first planet discovered since the time of the ancient Greeks.since the time of the ancient Greeks.

Modern telescopes are often two or more telescopes Modern telescopes are often two or more telescopes combined together. The images from the different combined together. The images from the different telescopes are combined into a single image by a telescopes are combined into a single image by a super computer.super computer.

Adaptive OpticsAdaptive Optics A problem with telescopes on Earth is that the moving A problem with telescopes on Earth is that the moving

atmosphere distorts the image of the stars and planets; atmosphere distorts the image of the stars and planets; that’s why stars twinkle in the sky.that’s why stars twinkle in the sky.

A way around this problem is to build telescopes where A way around this problem is to build telescopes where the atmosphere is thinner like on mountain tops.the atmosphere is thinner like on mountain tops.

Another method is to have a computer measure the Another method is to have a computer measure the amount of distortion from the atmosphere and change amount of distortion from the atmosphere and change the shape of the mirror or lens to compensate for the the shape of the mirror or lens to compensate for the effect of the moving atmosphere. This is called effect of the moving atmosphere. This is called adaptive opticsadaptive optics and an example of A.O. is the New and an example of A.O. is the New Technology Telescope (Technology Telescope (NTTNTT) in Chile.) in Chile.

To avoid the problem of the atmosphere completely is To avoid the problem of the atmosphere completely is to have a telescope out of the atmosphere completely. to have a telescope out of the atmosphere completely. This was the reason the Hubble Space Telescope was This was the reason the Hubble Space Telescope was built. Having no atmosphere has led to much more built. Having no atmosphere has led to much more detailed images.detailed images.

TriangulationTriangulation

Triangulation is the method of using Triangulation is the method of using a triangle’s geometry to calculate the a triangle’s geometry to calculate the distance to an object you can’t distance to an object you can’t reach, such as a star. reach, such as a star.

TriangulationTriangulation

Step 1: Create a baseline. Create two Step 1: Create a baseline. Create two points as far away from each other points as far away from each other as possible where you can still see as possible where you can still see the distant object. The longer the the distant object. The longer the distance between the two points, the distance between the two points, the more accurate the measurement.more accurate the measurement.

Triangulation Cont’dTriangulation Cont’d

Step 2: Measure the angles from the Step 2: Measure the angles from the end of the baseline. Use a protractor end of the baseline. Use a protractor to calculate the angle to the distant to calculate the angle to the distant object. With stars you need an object. With stars you need an astrolabe and compass to calculate astrolabe and compass to calculate the azimuth-altitude coordinates of the azimuth-altitude coordinates of the star.the star.

Triangulation Cont’dTriangulation Cont’d

Step 3: Make a scale drawing of the Step 3: Make a scale drawing of the triangle you made. Use a protractor triangle you made. Use a protractor to draw in the correct angles and a to draw in the correct angles and a ruler to accurately draw out the scale ruler to accurately draw out the scale model baseline. Make sure you model baseline. Make sure you choose a suitable scale factor. The choose a suitable scale factor. The altitude of the triangle is the nearest altitude of the triangle is the nearest distance to the distant object.distance to the distant object.

Triangulation Cont’dTriangulation Cont’d When triangulating the When triangulating the

distance to stars, the distance to stars, the largest baseline we can largest baseline we can use is the orbit of the use is the orbit of the Earth. Therefore the two Earth. Therefore the two angle measurements must angle measurements must be made six months apart.be made six months apart.

ParallaxParallax is the apparent is the apparent change in position of the change in position of the stars as the Earth moves stars as the Earth moves along in its orbit.along in its orbit.

A limitation of triangulating A limitation of triangulating is that it can only be used is that it can only be used on nearby stars.on nearby stars.

Big DistancesBig Distances An astronomical unit (AU) is a unit of An astronomical unit (AU) is a unit of

distance. It represents the distance from distance. It represents the distance from the sun to the Earth (150 million km). the sun to the Earth (150 million km).

1 AU = 150 million km. 1 AU = 150 million km. For example the distance of Pluto to the For example the distance of Pluto to the

sun is 40 AU. The distance of the nearest sun is 40 AU. The distance of the nearest star to the sun is about 271000 AU.star to the sun is about 271000 AU.

An even bigger unit of distance is the light An even bigger unit of distance is the light year. It represents the distance that light year. It represents the distance that light covers in one year. Since light travels at covers in one year. Since light travels at 300’000 km/s this is a very large distance, 300’000 km/s this is a very large distance, about 63’000 AU or 9.5 trillion km. The about 63’000 AU or 9.5 trillion km. The North Star is 431 ly away from us.North Star is 431 ly away from us.